In recent years, wireless communications technology available to mainstream users has undergone vast improvements in terms of data rates, quality, reliability, services offered, etc. With the advent of third generation (3G) technology, the public now widely enjoys mobile Internet, email, text messaging, video games, etc. on cell phone type devices. As technology advances, existing wireless protocols are updated and new ones are developed. Still, it is desirable to empower relatively older mobile equipment that operates according to earlier protocols, to function within updated networks operating with the latest protocols.
Over the past decade, there have been primarily two standards-based technologies for mobile communications: 3GPP-based technologies (also known as GSM/UMTS), and 3GPP2, which is CDMA based. GSM/UTMS is generally a TDM based technology, but also encompasses WCDMA (wideband CDMA). 3GPP2 type CDMA has evolved from the IS-95 standard based systems in the 1990's, to so-called 1xRTT or “cdma2000” (based on IS-856/IS-2000 standards) in the early 2000's. 1xRTT stands “for one times radio transmission technology” where the “1x” legend is used to denote the same bandwidth channel as IS-95, i.e., 1.25 MHz. 1xRTT is considered by some to be a 2.5G technology. Subsequently, a 3G technology called HRPD (High Rate Packet Data), also known as EVDO (Evolution-Data Optimized) was developed to succeed 1xRTT in the cdma2000 family, and has been widely deployed. HRPD provides higher data speeds than 1xRTT, typically 1.8-3.1 Mb/s versus 144kb/s for 1xRTT. HRPD also differs from 1xRTT in that its back-end network is entirely packet based, as opposed to the circuit based network of 1xRTT. HRPD has already undergone several revisions, i.e., Revs. 0, A and B.
In coming years, fourth generation (4G) technology, commonly known as Long Term Evolution (LTE), is expected to come of age. LTE is designed to provide yet higher data rates, higher efficient use of the radio network, and so on, to allow for enhanced multi-media services. The LTE evolution involves a transition to an all-IP core network with a simplified architecture and open interfaces. This requirement is defined by the System Architecture Evolution (SAE), which is the 3GPP specification for changes to the packet core network architecture. SAE is also known as Evolved Packet Core (EPC). GSM/UMTS based operators have a more natural evolution to LTE than do CDMA2000 operators.
Many CDMA2000-based operators are strategically migrating to an LTE network through a system known as 3GPP2 Evolved HRPD (eHRPD). With eHRPD, the mobile operator can upgrade their existing HRPD packet core network using elements of the SAE/EPC architecture. An objective is to provide seamless service mobility between HRPD and LTE access networks with a single mobility management protocol. eHRPD is being standardized as a method of interworking multiple access networks (eHRPD, E-UTRAN).
3GPP2 specifications such as 3GPP2 X.50057 and 3GPP2 A.S0022-0 have been developed and published to standardize the connectivity and interworking between E-UTRAN (LTE) and eHRPD. (E-UTRAN is the 3GPP Evolved Universal Terrestrial Radio Access Network.) The current interworking solutions, however, have not achieved perfection. Errors that may occur during data communication establishment and session procedures have led to a number of situations in which data communications fail and the subscriber simply cannot obtain desired data.
Accordingly, a need exists to improve interworking between wireless communications systems that are comprised of multiple protocol based equipment.